Hi there,
I also have a needle phobia after a needle broke in my arm during a tetanus jab aged 10.
Don't worry about it at all, the staff at your medical are very understanding, and totally made my relax. The only thing they will do with a needle is take a pinprick of blood from the top of your index finger, the device they use is just a small plastic thing, with a tiny needle in it, you don't even see the needle, they press it on your finger, and you are done!
Honestly, I harldy felt a thing, it is no where neer as bad as getting a needle from the doctor, beleive me, I once woke up panicing, in a sweat, about my tetanus jag, that was 5 years away!!!
Just tell the nurse at the medical centre about your phobia, and you will be fine, they will take good care of you.
Good luck.